The present invention relates to a device for driving a spindle mounting slide in a machine tool.
The invention relates in particular to a counterweight device for the drive of a slide that carries a spindle mounting head in a machine tool supported by a frame and controlled by linear motors that drive the tool along one or more axes.
Some automatic machine tools known in prior art comprise a linear electric motor which provides at least the vertical drive for the mounting slide. The linear electric motor comprises a rotor, also known as primary member or simply “primary” and a stator, also known as secondary member or simply “secondary”, the primary being integral with the mounting slide, and the secondary being integral with the vertical slideway of the slide.
The spindle mounting slide is usually connected to a counterweight device designed to balance the mounting head and slide unit during its vertical movement.
Experiments have shown that, in prior art machines of the type described above, the counterweight device does not effectively balance the mounting head and slide unit if the total weight of the unit is changed, for example when the head is removed for tool substitution or during maintenance.
This problem is felt all the more strongly with linear electric motors which cannot generate very strong drive power, especially for movements along the vertical axis.
Thus, when the tool mounting head is substituted, the linear motor is unable, for example, to compensate for the sudden decrease in weight due to the removal of the head because the latter may weigh even more than the power that the motor itself can generate.
The aim of the present invention is to overcome the above mentioned disadvantage by providing a device for driving a spindle mounting slide equipped with a counterweight device capable of effectively balancing the mounting head and slide unit even when the weight of the latter changes.